2005 Pontiac Montana - lost 1/2 tank gas

I filled my car up with gas. WEnt less then 10 miles watching the gas go to 1/2 tank!!! Can smell no leak in engine area, nothing on ground under car.

do you have a check engine light on?
Pontiac Montana P0463: Fuel Level Sensor Circuit → High Input | Drivetrain Resource (700r4transmissionhq.com)

So, you used 10 gal in 10 min? 1 gal per minute? I would look under van. Puddle? Go to gas station and fill up again. Are you down 10 gal?

So did you ACTUALLY lose 10 gallons… or did the gauge drop that fast? This is an older GM van and the fuel level sensors were notorious for becoming inaccurate because of buildup. I’ll bet if you try and fill your van up, it won’t take 10 gallons into the tank. In fact, you should try to fill it up right now to determine if it will or won’t take 10 gallons.

If it won’t take 10 gallons, add a can of Techron injector cleaner from an auto parts store to the tank. Should fix up the fuel gauge reading after one tank of gas.

If it WILL take 10 gallons, get the van into a service shop ASAP, you have a huge leak or are dumping it through the engine. Neither are good!


I assume your fuel gauge has become inaccurate, and you didn’t actually use a half tank of fuel in 10 miles. The only way you could possibly use that much fuel in such a short distance would be an external leak, and you would smell it. I have owned cars in the past where the fuel line rusted through underneath, or a leak occurred at the inline fuel filter underneath, and the odor becomes readily apparent, even while the leak is small.

If you’re sure that there is no leak, try topping off the fuel and see how much it takes. My guess is that it’s still almost full, and the fix is going to be a new fuel pump assembly–and make sure to buy a good one, not a cheap one.

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Almost surely a gas gauge that has gone wonky.


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Was that fast and furious 17 where they siphoned a moving tanker in a following truck? And driver of tanker had no clue?
I think that happened to your van.

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LOL…10 characters

More than 10 if true since the Montana has a 25 gallon tank. Any significant loss of fuel in a relatively short time with no other symptoms is unlikely. My money’s on a flaky gauge/sending unit.

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1/2 tank of gas in 10 miles? hmmm … The engine wouldn’t be able to run if that much fuel was being delivered to the cylinders. The gasoline either has to be leaking out and falling on the ground, or there’s a problem w/the fuel gauge. I suppose its possible the leak only occurs when the car is moving, which prevent any pudding underneath the car. But you’d think there would be a noticeable fuel odor then. So my guess is the gauge reading is incorrect. Good chance the fuel level sender’s float is no long floating.

DOA, :laughing:

Brenda made one post 2 days ago and has not even returned to answer any questions so why even speculate what might be wrong .


Yep another drive by never to be seen again.


That’s because she has to go back to the gas station to refill the tank several times each day.


YOU ARE IGNORANT AND RUDE. THis is my first time here. SORRY I DID NOT MEET YOUR NEEDS FOR a PAT on the back. THanks you to everyone for your help. My mechanic figured it to be the float. I AM OLD AND NOT A MECHANIC> THANK YOU


@Brenda29 - Volvo-V70 is rude. I apologize on behalf of him, because he isn’t likely to do it…

Glad you were able to get your car figured out, and it looks like most of the advice here was pretty spot on and helpful. :slight_smile: